Covalent Organic Framework/Aluminum Oxide Composite Nanosheets as a Separator for High-Performance Lithium–Sulfur Batteries

With the depletion of fossil energy and increasingly serious environmental pollution, the development of renewable sources of energy is imminent. Exploration of high-efficiency energy storage and transformation materials has become the focus in the field of energy research. Covalent organic frameworks (COFs), as a kind of porous and crystalline polymer, have attracted extensive attention. In this work, we developed a composite material (Al2O3-G-COFSO3) using COFs and alumina, which can serve as an efficient separator in lithium–sulfur (Li–S) batteries. In the composite, alumina can improve the transport ability of Li+ and thus improve conductivity and SO3–COF can effectively restrain the shuttle of polysulfides by electrostatic repulsion. At a current density of 0.05C, the composite-based battery exhibited a high capacity of 1404 mAh g–1, which ranks as one of the highest values among all of the COF-based Li–S batteries. Even at a discharge rate of 1C, it can also achieve a high experimental capacity of 999 mAh g–1 with a low decay rate of 0.061% over 500 cycles. Moreover, the battery also showed a high electrochemical stability and long-term performance stability.